Epidemiologic studies conducted over the past 25 years have established the Type A Behavior Pattern (TABP) as having an independent association with coronary heart disease (CHD). Despite its demonstrated strong construct validity, inadequate information is available about its stability over time. It is therefore proposed to investigate the extent of changes in TABP in relation to aging and changing environmental milieu over a 10-year period in a cohort of adult, male twins, who comprised the California subgroup of the National Heart, Lung, and Blood Institute Twin Study conducted in 1971 and who were reexamined in 1981. The specific aims of this proposal are: (1) to determine the cross-sectional relationships at baseline and follow-up examinations between the TABP, health habits, psychosocial factors, physiological and biochemical risk factors for CHD; (2) to examine the predictive relationships of intake TABP and related psychosocial variables to changes in other risk factors for CHD over time; (3) to determine the extent of changes over time in TABP and its components in relation to changes in occupational and health status; (4) to assess genetic and environmental continuiuty of CHD risk factors. Longitudinal investigations of this behavior and its relationship to other CHD risk factors and aging have not heretofore been carried out. The proposed research provides this needed type of longitudinal investigation. Moreover, the subjects by virtue of their being adult twins provide unique opportunities for controlling effects of both heredity and early familial environment in the later manifestations of risk factors.